The present invention relates to a process and apparatus for forming shaped lumps from coke fines and charcoal fines or dross.
The production of coke in general has the object to provide for a fuel with a highly reactive surface and a concentrated contents of carbon. For metallurgical processes such as those in a blast furnace, coke is required having a specific pressure resistance, abrasion resistance and reactivity. Besides, the coke should have a uniform minimum lump size.
These requirements can be met only if for the coke production coal types are selected by conventional methods. These types, however, amount only to about 10% of the normal coal supply. The coal industry has therefore developed processes by which the coke, particularly shaped coke such as briquettes, is made from highly volatile poorly baking or not baking coal types or mixture of these coal types to which coke fines or dross may be added.
These coal types are formed into briquettes after a thermal pretreatment or upon addition of binding agents and are subjected to a thermal hardening treatment or low temperature burning. (Federal Republic of Germany: Pat. No. 881,188; Published application No. 1,180,713; Pat. No. 834,691; Pat. No. 852,835; Pat. No. 1,031,798; Published application No. 1,696,509, and Published application No. 2,358,122).
Shaped coke bodies have also been made from fine grain size coking or non-coking coal or coke fines to which solid and/or liquid binding agents may be added by means of pelletizing trays or in pelletizing drums while subjecting the material to a rolling or rolling-off movement. These pellets are then subjected to coking and hardening or firing possibly after predrying. (Federal Republic of Germany: Published applications Nos. 1,571,703, 1,571,698 and 1,671,366).
The drawbacks of these processes are mainly that they must be carried out in several stages and apparatus and that a large amount of energy is necessary for the thermal heating or coking steps.
The briquetting process also limits the gas permeability of the shaped coke by a comparatively dense outer layer. Coke pellets on the other hand are not up to highest standards in regard to their mechanical resistance and their uniformity of lump size.
The processes are also generally limited to particular types of coal as already mentioned and permit only use of small amounts of coke dross or permit use only of coke dross of a very fine and uniform grain size.
In the production of steels of high purity, charcoal has also been used as the reducing agent in the blast furnace. In this case about 10% of the amount of charcoal result in charcoal dross or fines which, with the processes of the prior art, cannot be turned to use at reasonable expense.
The process of the invention therefore has the object to permit forming lumps of uniform size with a desired porosity and strength in a single continuous process from a slurry made of a mixture of coke fines or coal fines and a conventional binding agent.